Are there formulas I can use
Yes, but you cannot use a formula without having numbers to plug in.
or anyone have a general idea as far as torque, etc I would need for a standard size go kart? The 250-300 oz-in range?
You need to measure how much torque is needed - directly where you're going to interface the steering.
If you mount an arm at that place and use a luggage scale, pulling the arm in a known distance from the center of the axle you're turning (and with the pull direction 90°to the arm at all times, you find the torque needed. when that's done, get back with the result.
A drawing on how you're gonna make the mechanical interface would help things along as well.